1. Field of the Invention
The present invention relates to a magnetic head device comprising a piezoelectric element.
2. Description of the Related Art
FIG. 6 is a plan view showing an example of a conventional hard disk device. The hard disk device shown in FIG. 6 comprises a magnetic disk 101, a spindle motor 102 for driving the magnetic disk 101 to rotate, a carriage 103, a load beam 104, a slider 105, and a voice coil motor 106. A magnetic head device schematically comprises the load beam 104 and the slider 105.
The base end 104b of the load beam 104 serving as a supporting member is connected to the tip 103a of the carriage 103 comprising a rigid material, and the slider 105 is mounted at the tip 104a of the load beam 104 through a flexure (not shown in the drawing).
The carriage 103 and the load beam 104 are driven in the radial direction of the magnetic disk 101 by the voice coil motor 106 to perform the seek operation of moving a reproducing element and recording element mounted on the slider 105 onto a desired recording track, and the tracking operation of finely controlling the positions of the reproducing element and the recording element to keep them on a center line of the recording track.
Furthermore, a microactuator is mounted on the load beam 104 so that only the tip of the load beam 104 can be moved by the microactuator to perform the tracking operation.
FIG. 7 is a perspective view of the load beam 104, and FIG. 8 is a sectional view showing the principal portion of the load beam 104 shown in FIG. 7.
The load beam 104 is made of a stainless steel leaf spring material, and comprises a fixed base end 111a held by the carriage, and an oscillating portion 111b oscillatable horizontally relative to the fixed base end 111a. The load beam 104 further comprises arms 111c formed on both sides of the front end of the fixed base end 111a to extend in the longitudinal direction of the fixed base end 111a. The oscillating portion 111b is connected to the arms 111c through elastic supporting portions 111d. 
Furthermore, piezoelectric elements 112 and 113 serving as microactuators are placed over a void 111e between the oscillating portion 111b and the fixed base end 111a. 
The piezoelectric elements 112 and 113 comprise piezoelectric layers 112a and 113a made of a piezoelectric material such as lead titanate zirconate (PTZ), and electrode layers 112b and 112c, and electrode layers 113b and 113c, respectively, made of gold films formed above and below the piezoelectric layers 112a and 113a. 
As shown in FIG. 8, the electrode layers 112c and 113c of the piezoelectric elements 112 and 113 are bonded to the oscillating portion 111b and the fixed base end 111a with an adhesive resin 115
In FIG. 7, reference numeral 121 denotes a slider mounted at the tip of the oscillating portion 111b through a flexure (not shown in the drawing).
The piezoelectric elements 112 and 113 are elements which produce strain when a voltage is applied through the electrode layers 112b and 112c, and the electrode layers 113b and 113c, respectively.
The piezoelectric layers 112a and 113a of the piezoelectric elements 112 and 113 are polarized in the thickness direction, but the polarization directions of the piezoelectric elements 112 and 113 are opposite to each other. Therefore, when the same potential is applied to the electrode layers 112c and 113c, one of the piezoelectric elements extends in the longitudinal direction, while the other piezoelectric element shrinks in the longitudinal direction.
As a result, the elastic supporting portions 111d are deformed to change the position of the slider 121 mounted at the tip of the oscillating portion 111b. Namely, the slider 121 mounted at the tip of the oscillating portion 111b can be finely moved in the track width direction to perform the fine tracking operation.
Particularly, the precision of the tracking operation must be increased as the recording density of the magnetic disk 101 increases. However, the load beam 104 enables the precise tracking operation, and is thus adaptable for improving the recording density.
As the adhesive resin 115 for bonding the piezoelectric elements 112 and 113 and the oscillating portion 111b and the fixed base end 111a, a thermosetting epoxy resin is conventionally used. The epoxy resin is roughly classified into a one-component type and a two-component type.
However, unlike a photo-curing type, a thermosetting epoxy resin cannot be temporarily hardened by light irradiation, and thus a bonded portion must be fixed by a jig or the like until curing is completed, thereby causing the problem of deteriorating manufacturing efficiency.
With a one-component epoxy resin, a powdery curing agent is added to an epoxy solution as a main agent, and then dispersed in the epoxy solution by heating to start curing. However, the viscosity of the epoxy solution decreases until the temperature is increased to the curing temperature, thereby making the mixed state of the curing agent and the epoxy solution heterogeneous to leave an uncured portion in some cases. The uncured portion causes the occurrence of out gases, spots due to dissolution and re-adhesion of the uncured portion, etc., causing the problem of deteriorating the reliability of a magnetic head device.
With a two-component epoxy resin, unlike the one-component epoxy resin, the uncured portion does not occur. However, the viscosity greatly varies with time during mixing of the main agent and the curing agent, thereby causing the problem of complicating handling of the resin after mixing.
Therefore, in order to solve the above problems, the use of a photo-curing and thermosetting acrylic adhesive resin has recently been investigated. The acrylic adhesive resin is cured by radical polymerization, but peroxide radicals occur due to contact with atmospheric oxygen to cause reaction deactivation inhibition. This causes the problem of increasing the amount of the out gases produced, and deteriorating humidity resistance and heat resistance to deteriorate the reliability of the magnetic head device.
In consideration of the above-described present conditions, it is an object of the present invention to provide a magnetic head device having excellent reliability and comprising a piezoelectric element and a load beam which are bonded together in a good state without using a jig.
In order to achieve the object, the present invention has the following construction:
A magnetic head device of the present invention comprises a slider comprising a reproducing element for detecting magnetic signals recorded on a recording medium, and a recording element for recording magnetic signals on the recording medium; an elastic supporting member for supporting the slider; and a piezoelectric element mounted on the elastic supporting member, for deforming the elastic supporting member to change the position of the slider, wherein the piezoelectric element and the elastic supporting member are bonded together with a photo-curing and thermosetting epoxy adhesive resin having a Young""s modulus of 1 GPa or more at 25xc2x0 C., and a glass transition temperature of 90xc2x0 C. or more.
In the magnetic head device of the present invention, the piezoelectric element and the elastic supporting member are bonded together with the photocuring and thermosetting epoxy adhesive resin, and thus the adhesive resin can be temporarily cured by light irradiation to temporarily fix the piezoelectric element without using a jig or the like, thereby increasing manufacturing efficiency.
Unlike an acrylic resin, an epoxy resin as a main component of the adhesive resin is cured by cationic polymerization, and thus does not produce reaction deactivation inhibition due to oxygen, thereby increasing the reliability of the magnetic head device.
Furthermore, since the Young""s modulus at 25xc2x0 C. is 1 GPa or more, and the glass transition temperature is 90xc2x0 C. or more, rigidity of the adhesive resin can be kept high in the practical temperature region of 90xc2x0 C. or less. Therefore, the piezoelectric element and the elastic supporting member are bonded together through a rigid material, permitting secured propagation of a displacement of the piezoelectric element to the elastic supporting member, and the precise tracking operation.
In the above-described magnetic head device of the present invention, the elastic supporting member comprises a fixed base end and an oscillating portion which is connected to the fixed base end to support the slider and which can be oscillated by the piezoelectric element relative to the fixed base end. The piezoelectric element is bonded by the photocuring and thermosetting epoxy adhesive resin so as to be placed over the space between the fixed base end and the oscillating portion.
In the magnetic head device, the piezoelectric element is bonded to the fixed base end and the oscillating portion by the photocuring and thermosetting epoxy adhesive resin, and thus the piezoelectric element is bonded to the fixed base end and the oscillating portion through a rigid material, thereby permitting a precise displacement of the oscillating portion due to the piezoelectric element.